The present disclosure is directed toward a method and an apparatus for providing a perceived texture on a substantially uniform print media substrate. More specifically, the textured appearance is provided on a print of a primary image using a clear toner applying component for low coverage portions of the primary image and a pigmented toner applying component for high coverage portions of the primary image.
A textured substrate is a print media having a noticeable third dimension resulting from raised pattern portions. Textured substrates are used to provide an attractive appearance in products, such as, business cards, greeting cards, scrapbook pages, wallpaper, wrapping paper, and other paper and fabric-based merchandise. The techniques and materials used to produce the textured patterns may add significantly to the production costs. In addition to higher consumer costs, textured substrates tend to provide less sharp results during electronic printing. For example, text can be illegible if it is printed on rough textured patterns. Traditional printing techniques, utilizing a press, provide clear text results on textured substrate because an inked surface of the press contacts the textured print media. However, ink or toner materials used for electronic, laser, digital, and xerographic printing techniques are lightly applied to the substrate. The toner or ink tends to not reach recessed portions of the substrate surface. Because consumer image forming devices situated in homes and offices generally print using electronic methods, there is a need for providing a textured appearance on uniform substrates.
One approach for providing a perceived texture on a uniform print media substrate includes applying a layer of clear toner over portions of a print of a primary image that are desirably raised relative to recess portions. In another approach, the print of the primary image is rendered at variable screen angles. A first halftone dot orientation is rendered onto the uniform substrate to represent the raised portion and a second, different halftone dot orientation is rendered onto the substrate to represent the recessed portion. Generally, a gloss differential between the raised and recessed portions provides a perceived texture on the uniform substrate.
In conventional glossmark applications, the gloss differential is achieved by alternating between two halftone types that are selected to have similar density characteristics while displaying distinctly different anisotropic structure orientations. However, rendering of the desired glossmark is only effective where the halftone structures in the primary image can be changed significantly without altering the visual colors and densities. Very low density areas, such as background areas and highlight areas, display minimal to no differential gloss effect, thus rendering any desired perceived texture placed thereupon invisible due to the absence of colored toner. Fully saturated areas, on the other hand, require complete toner coverage. The anisotropic halftone dot gloss structure, and therefore the perceived texture, is lost.
One approach for enhancing gloss differential at high and low coverage areas includes applying clear toner coincident with a select one anisotropic halftone screen. Another approach for enhancing the glossmark across a low coverage area is to apply a low density pattern of light color to all low density areas of the halftone image. A further approach includes applying an under-color to all high density areas in the halftone image. The underlying color halftone structure modifies the gloss.
A problem with these gloss enhancement approaches is that they do not consider an additional layer of information representative of the texture element. Texture is represented as various degrees of shading in a two-dimensional copy of a three-dimensional substrate. In one embodiment, the raised and recessed portions of the original textured substrate can be represented by different luminance values in the textured image data. The brightness is the toner density.
Therefore, there is needed a system that can distinguish between a low toner coverage corresponding to a color of the primary image and a low toner coverage corresponding to a degree of shading (i.e., a degree of dimension) of the textured image. In this manner, a perceived texture can be evenly discernable across an entire output image despite descriptions in the primary image data.